Answer: Option 'a'and 'd' are true.
Explanation:
Inverse matrices are those matrices for their always exist a square matrix
such that

Matrix should have non zero determinant for getting inverse of it.
An inverse matrix should be square matrix.
Inverse of matrix can be calculated by two approaches:
1) Adjoint method
2) Row/Column elementary method
Hence, Option 'a'and 'd' are true.